Which of the following is the PRIMARY biochemical marker of protein deficiency in protein-energy malnutrition?

Explanation

## Biochemical Markers of Protein Deficiency **Key Point:** Prealbumin (transthyretin) is the most sensitive and specific marker of protein nutritional status because of its short half-life (2–3 days) and rapid response to changes in protein intake. ### Why Prealbumin is Superior | Marker | Half-life | Sensitivity | Clinical Use | |--------|-----------|-------------|---------------| | Prealbumin | 2–3 days | High | **Gold standard for acute protein depletion** | | Albumin | 20 days | Moderate | Reflects chronic malnutrition | | Total protein | Variable | Low | Non-specific | | BUN | Hours | Low | Reflects renal function, not protein status | **High-Yield:** Serum albumin, while commonly measured, has a long half-life (20 days) and is influenced by liver synthetic function, inflammation, and fluid status—making it less specific for protein deficiency alone. **Clinical Pearl:** In acute protein-energy malnutrition (PEM), prealbumin drops within 48–72 hours, whereas albumin may remain normal for weeks. This makes prealbumin the preferred marker for monitoring nutritional intervention response. **Mnemonic:** **PRAT** = Prealbumin Reflects Acute Turnover (short half-life, rapid response).